Fig. 6.

Effects of wild-type ubiquitin and ubiquitin mutants on OAT1 ubiquitination. (A) cDNA for HA-tagged wild-type ubiquitin (Ub), ubiquitin mutants UbΔG, Ub-K48R, and Ub-K63R were transfected into COS-7 cells, respectively, followed by treatment with or without PMA for 30 minutes. The treated cells were lysed. OAT1 was immunoprecipitated by anti-myc antibody, followed by immunoblotting with anti-HA antibody. (B) densitometry plot of results from (A) as well as from other experiments. Ubiquitinated OAT1 in PMA-treated cells was expressed as the percentage of that found in control cells. The values are mean ± S.E. (n = 3).